Process for the production of acetylene



May 25 1954 w. s. DoRsEY PROCESS FOR THE PRODUCTION oF ACETYLENE FiledApril 9, 1951 2 Sheets-Sheet l 2 A a i M 22% 2 5 2 oooooooo oooo oo oooooo u Nm I Y .QJ M a nd.

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25, 1954 W, s, DORSEY 2,679,542

PROCESS FOR THE PRODUCTION OF A CETYLENE Filed April 9, 1951 2Sheets-Sheet 2 fcw -1 n 4% Patented May 25, 1954 UNITED STATES PROCESSFOR THE PRODUCTION OF ACETYLENE William Smith Dorsey, Fullerton, Calif.,assignor to Union Oil Company of California, Los Angeles, Calif., a

corporation of California Application April 9, 1951, Serial No. 219,936

14 Claims.

This invention relates to a process for the production of acetylene, andin particular concerns an improved process for the manufacture ofacetylene by the partial oxidation of hydrocarbons.

In the co-pending applications of John L. Bills, Serial No 178,132, ledAugust 7 1950, and

described a process whereby acetylene is produced by preheating areactant gas mixture comprising a hydrocarbon and oxygen, admixinghydrogen with the preheated gas mixture whereby an exothermic reactionoccurs with a consequent increase in temperature to about 1100"- 1500C., and thereafter quench cooling the resulant hot product gas to arelatively low temperature Within a very short period of time. rThepreheat temperature the exothermlc heat of the reaction itself andwithout the addition of any further substantial quantity of heat. Thisprocess is highly effective in securing relatively high yields ofacetylene based on the quantity of hydrocarbon consumed, and isparticularly attractive from the standpoint of chemical cost since airmay be employed as the source of oxygen and the hydrocarbon may below-cost natural gas. Also, thermal requirements are lower than those ofprior art partial oxidation processes since lower preheat temperause ofhydrogen in the manner specified to initiate the acetylene-producingreaction, and the various advantages of the process cannot be realizedby omitting the hydrogen addition step or by admixing the hydrogen withthe reactant gas mixture prior to preheating. There is no overallconsumption of hydrogen in the process, however, and under usualconditions of operation the product gas often contains more hydrogenthan was originally added to the preheated reactant gas, i. e., theprocess results in a net production of hydrogen. Accordingly, the use ofhydrogen in the stated manner does not add to the chemical costsinvolved since such hydrogen may be recovered from the product gas andrecycled back to the reaction zone indefinitely. However, it is usuallynecessary to recycle from to l|0 volumes of hydrogen per volume ofacetylene produced, and even though the hydrogen may be employed inadmixture with certain other components of the product gas, the cost ofseparating and handling this quantity of hydrogen constitutes a verymaterial part of the total cost of producing acetylene by this process.Any means by which the amount of hydrogen employed can be reducedwithout sacrificing the other economic and operational advantages whichare characteristic of this process would be of great value in providinglow-cost acetylene from cheap natural gas or It is accordingly an objectof the present invention to provide means whereby the amount of hydrogenrequired in the aforesaid acetylene process may be materially reduced.

Another object is to provide a means for effecting a significantreduction in the cost of producing acetylene by the partial oxidation ofhydrocarbons.

A further object is to provide an improved process for the manufactureof acetylene from natural gas or methane and air.

Other objects will be apparent from the following detailed descriptionof the invention, and various advantages not specically referred toherein will be apparent to those skilled in the art upon employment ofthe invention in practice.

I have noW found that the above and related objects may be realized in aprocess whereby the added hydrogen is employed to form a gaseous layeror lm along the walls of a reaction zone into which the preheatedreactant gas is introduced in a plurality of separate streams. Moreparticularly, I have found that the amount of hydrogen required tosecure the unique advantages oi" the aforesaid process may be verysubstantially reduced by preheating the reactant gas in a plurality ofseparate streams and introducing the streams of preheated gas into thecentral or axial portion of a common reaction zone while introducinghydrogen into the reaction zone adjacent the periphery thereof so that agaseous lm comprising hydrogen is interposed between the walls of thereaction zone and at least the major portion of the preheated reactantgas entering the reaction zone. By operating in such manner, the amountof hydrogen supplied per volume of acetylene produced may be reduced byone-half or more without adversely affecting the acetylene yields andheat requirements or causing the deposition of any substantial quantityof carbon black within the reactor. over, even though the amount ofhydrogen introduced into the reaction zone in the present process isconsiderably less than that which must be employed in the prior hydrogenaddition process, the amount of hydrogen in the product gas issubstantially the same. Thus, the present process produces considerablymore hydrogen than is required for its operation, and separation of thesmall amount of hydrogen required for recycling purposes from theproduct gas is relatively simple and inexpensive.

The manner in which such mode of procedure operates to secure theseresults is not known with cetrainty, but it is postulated that mixing ofthe hydrogen and reactant gas takes place in a relatively narrow zonesurrounding their nominal boundary, thereby effecting within such zonethe acetylene-producing reaction referred to above, and that theexothermic heat of this reaction raises the temperature of the morecated portion of the reactant gas where the conventional partialOxidation reaction occurs within this portion of the gas in thesubstantial absence of hydrogen. The latter reaction is usuallycharacterized by the deposition of large quantities of carbon on thewalls of the reaction zone, but in the present instance the body of gasundergoing this reaction is separated from the walls o the reaction zoneby a lm of hydrogen, and carbon black deposition is substantiallyprevented. It is to be understood, however, that the invention is notlimited by these postulations concerning the possible mechanism of itsoperation.

The process of the invention will be more clearly understood byreference to the accompanying drawings which form a part of thisspecification. n said drawings:

Figure l represents a longitudinal cross-sectional view of .a simplereactor which may be employed in the practice of the invention.

Figure 2 represents a transverse cross-sectional view of this reactortaken along line 2-2 of Figure l.

Figure 3 represents a longitudinal cross-secr tional view of a somewhatdifferent reactor suitable for use in practicing the invention on asomewhat larger scale.

Figure 4 represents a transverse cross-sectional view of this reactortaken along line 4-4 of Figure 3.

Referring now to Figures 1 and 2, in which like numerals designate likeparts, the illustrated reactor comprises a vertically disposedcylindrical vessel having refractory side-walls I0, an upper end closureII and a conical bottom closure I2. Side-walls Ii! are surrounded by alayer of thermal insulation I3 held in place by jacket It. Within thevessel, a transverse refractory partition I5 supported by ring I6divides the enclosed space into a preheating zone I'I and a reactionzone I8. Heating element I9, diagramniatically shown as an electricheating coil, is positioned around the walls of preheating zone I1 tosupply heat thereto. End closure I I and transverse partition I5 areprovided with coaxial holes to receive opposite ends of a plurality ofpreheating tubes 2i! arranged in concentric circular pattern.

rFubes which are peripherally located, i'. e., adjacent the walls ofreaction zone I8, are shown terminating at partition I5, whereas thosemore centrally located are shown extending into reaction zone i8 a shortdistance and those most centrally located are shown extending evenfarther into the reaction zone. Alternatively, all of the preheatingtubes may be of the same length. Header 2l closes off the upper end ofthe reactor and forms a reactant gas introduction zone 22 whichcommunicates by means of reactant gas inlets 23 with manifold 2d.Preheating tubes 20 thus communicate between introduction zone 22 andreaction zone ISS, and traverse preheating zone Il. Positioned coaxiallyaround those of preheating tubes 20 which are located adjacent to thewalls of reaction zone I8, i. e., the peripheral ring of preheatingtubes 20, are hydrogen introduction conduits 25 which communicate withreaction zone I8. Hydrogen inlets 2B communicate between hydrogenintroduction conduits 25 and manifold 21 which in turn is progas passingvided with a hydrogen supply line 28 leading from a source of hydrogen,not shown. The combination of supply line 2o, manifold 21, inlets 26,and conduits 25 permits hydrogen to be introduced into reaction zone I8in such manner as t0 form a ilrn comprising hydrogen between the wallsof reaction zone I8 and the preheated reactant gas which is introducedinto the reaction zone via preheating tubes 2B. Spray nozzles 29provided near the bottom of the vessel communicate by means of conduits'd to a source of quenching medium, e. g., water, not shown, and serveto quench the hot product gases issuing from the reaction zone. Aproduct gas withdrawal conduit @I is positioned below the spray nozzles,and communicates with product gas storage means, not shownl Conduit 32is provided at the bottom of the vessel for withdrawal of the quenchingmedium 33.

Operation of this reactor in accordance with the process of theinvention is carried out as follows: The reactant gas, which comprises asuitably proportioned rnixture comprising a hydrocarbon and oxygen, e.ff. a mixture of natural gas or methtane and air, is introduced intomanifold 2li and passes via inlets 23 and introduction zone 22 throughpreheating tubes 2G and into reaction zone I8. During passage throughtubes 2d, the reactant gas is raised to the necessary preheattemperature, e. g., 600-1150 C., heat being supplied from heatingelement I9. Simultaneously, hydrogen is introduced into manifold 2l fromsupply line 28, and passes via inlets 26 and conduits 25 into reactionzone I8. Since conduits 25 are positioned around the periphery of thevessel adjacent the walls thereof, the hydrogen forms a gaseous layer oriilm adjacent the walls of reaction zone I8. Within the reaction zonethe acetylene-producing reaction takes place as previously described,thereby forming a hot product gas which is quench cooled as it passesthrough the spray of liquid cooling medium supplied through spraynozzles 29. The cooled product gas is withdrawn through conduit 3| andpasses to gas storage means. The velocity of the through the reactor iscontrolled in accordance with the capacity and design of the reactor sothat the reactant gas is heated to the requisite pre-heat temperature bythe time it issues into the reaction zone from the preheating tubes, andso that the product gas is cooled to a temperature at whichsubstantially no further reaction occurs within the requisite shortperiod of time, as is more fully described below.

Considering now the essential operating details of the new process, thereactant gas consists essentially of a proportioned mixture of ahydrocarbon and oxygen. A wide variety of hydrocarbons are suitable, butbest results are obtained with non-aromatic hydrocarbons, particularlythose which are normally gaseous or liquid and boil below about 400 F.under atmospheric pressure. The term non-aromatic hydrocarbon is hereinemployed as a generic term including saturated and unsaturated aliphaticand cycloaliphatic hydrocarbons but excluding aromatic or benzenoidhydrocarbons. The normally gaseous saturated aliphatic hydrocarbons,particularly methane and natural gas, are especially preferred by reasonof their low cost and ease of handling. Hydrocarbon mixtures, e. g.,mixed renery gases and various petroleum distillates are also suitable.When employing a liquid hydrocarbon reactant, it is preferably vaporizedprior to its admixture with the oxygen and/or prior to being preheated,although such vaporization may be effected as a part of the preheatingstep. The oxygen reactant is pure oxygen itself,

reason of its lack of features of the process that the results obtainedemploying air are comparable or better than those of previous processesin which pure oxygen has been employed. The mole ratio of hydrocarbon tooxygen in the reactant gas varies between rather wide limits dependingupon the identity of the hydrocarbon. When the hydrocarbon is one ofrelatively high molecular weight, e. g., a petroleum distillate such askerosene, as many as 50 moles of oxygen should be provided per mole ofhydrocarbon. On the other hand, when the hydrocarbon is a normallygaseous saturated aliphatic hydrocarbon, e. g., methane, natural gas,ethane, etc., an excess of hydrocarbon is employed so that the moleratio of hydrocarbon to oxygen is suitably between about 1.33/1 andabout 3.0/1. Thus, the mole ratio of hydrocarbon to oxygen varies fromabout 0.02/1 to about 3.0/1 depending upon the nature of thehydrocarbon. When the oxygen reactant is in the form of air and thehydrocarbon is methane or natural gas, the reactant gas preferablycomprises between about 17 and about 30 per cent by volume of thehydrocarbon and, correspondingly, between about 83 and about 70 per centby volume of air. When the reactant gas comprises air and a petroleumdistillate such as kerosene, it may contain from about 4 to about l0 percent by volume of the hydrocarbon vapor and from about 96 to about 90per cent by volume of air. If desired, two or more reactant gascompositions may be employed, e. g., the reactant gas which isintroduced into the central portion of the reaction zone may be somewhatricher in the Ihydrocarbon component than the reactant gas which isintroduced near the peripheral lm of hydrogen.

The hydrogen which, according to the process of the invention, isintroduced into the reaction zone along the periphery thereof so as toprovide a gaseous layer or lm comprising hydrogen between the walls ofthe reaction zone and at least a major part of the reactant gas which isintroduced therein may be pure hydrogen or a Suitable mixture ofhydrogen and an inert gas which does not react with the other componentsof the system under the conditions existing in the reaction zone, e. g.,nitrogen, carbon monoxide, carbon dioxide, water vapor, etc. The termhydrogen-containing gas is herein employed as a generic term to includepure hyrogen as well as mixtures comprising free hydrogen and an inertgas. Employment of the hydrogen in admixture with an inert gas isusually more economical than the use of pure hydrogen, and in someinstances is more advantageous from an engineering standpoint. Theproduct gas for the most part comprises hydrogen, nitrogen and carbonmonoxide in addition to unreacted hydrocarbon and the acetylene product.While it is possible to separate all of these components insubstantially pure form and thus recover pure hydrogen for re-use in theprocess, it is much simpler to separate the hydrogen in admixture withpart of the nitrogen and/or carbon monoxide and to employ such mixtureas the hydrogen-containing gas which is introduced along the walls ofthe reaction zone. Thus, employing the hydrogen in the form of a mixturewith nitrogen or carbon gas from the product monoxide or both issuperior to employing the' hydrogen in pure form in instances where itis desirable to recover hydrogen from the product gas and re-use it inthe process. Such mixture may comprise as much as about 70 per cent b'yvolume of the inert gas. Accordingly, the hydrogen-containing gasemployed in the process may comprise from about 30 to 100 per cent byvolume of hydrogen and from about 70 to zero per cent by volume of aninert gas. Since the inert gas has a cooling effect within the reactionzone, the use of mixtures containing relatively'large proportions4 ofthe inert gas requires the use of higher preheat temperatures thenecessary high reaction temperature, thereby increasing the heatrquirements of the process. On the other hand, the cost of separatinghydrogen mixtures from the product gas increases with the concentrationof hydrogen in the separated mixture. Accordingly, the optimumcomposition of the hydrogen-containing gas will be determined bybalancing the cost of separating such gas against the cost of supplyingaddiitonal heat. Usually the optimum gas mixture will contain at leastabout per cent by volume of hydrogen and less than about monoxide.Preferably, but not necessarily, the hydrogen-containing gas ispreheated to substantially the same temperature as the preheatedreactant gas prior to its introduction into the reaction zone in themanner herein specified. The heating means employed may be the same asthose provided for preheating the reactant gas, or they may beindependent.

As previously stated, introduction of the hydrogen-containing gas intothe reaction zone in the particular manner herein described permits avery substantial reduction in the amount of hydrogen required to securethe advantages inherent in the general hydrogen-addition process.Heretofore, the hydrogen-containing gas was employed in an amountsuflicient to provide at least 0.5 mole, and preferably more than 1.5moles, of hydrogen per mole of hydrocarbon in the reactant gas. Byintroducing the hydrogencontaining gas into the reaction zone along thewalls thereof in the manner of the invention, however, only from about0.1 to about 1, usually from about 0.3 to about 0.6, moles of hydrogenneed be provided per mole of hydrocarbon. This amounts to a reductionor" about 8O per cent in the amount of hydrogen required, and since theproportion of hydrogen in the product gas is not substantially reduced,recovery of the required amount of hydrogen is greatly simpliiied. Insome instances it may permit dispensing entirely with the hydrogenrecovery and recycle operations, which has heretofore been economicallyunieasible.

It is essential to the successful operation of the process of theinvention that the reactant gas be preheated and introduced into thereaction zone in a plurality of relatively small streams, i. e., anumber of streams each of which has a cross-sectional area representingonly a small fraction of the cross-sectional area of the reaction zone.This requirement appears to be identified with the aforementionedprobability that the portion of the reactant gas which is located nearthe center of the reaction zone and farthest from the peripheral filmcomprising hydrogen may undergo a type of reaction in order to securewhich is more critically dependent upon the preheat temperature than thereaction which occurs in the presence of hydrogen. The number of streamsinto which the reactant is divided during the preheating will dependprimarily upon the capacity of the reactor and the heat transfercharacteristics of the preheating Zone thereof, but is usually at leastfour and may be as many as fifty or more.

The temperature to which the reactant gas is preheated prior to itsintroduction into the reaction zone is such that the temperatureattained in the reaction which is induced by introduction of thehydrogen into the reaction zone is between about 1100 C. and about 1500oC., preferably between about 1275 C. and about 1375 C. 1t is a uniquecharacteristic of the hydrogen addition process that the reactant gascan be preheated to relatively high temperatures, e. g. 6500-1150o C.,in the absence of hydrogen without reaction occurring to any substantialextent, but upon the introduction of hydrogen into the preheatedreactant gas an exothermic acetylene-producing reaction takes placespontaneously and without the addition of any further substantialquantity of heat. As a result of such exothermic reaction taking place,the temperature of the reacting gas increases very rapidly to much highvalues. Maximum yields of acetylene are attained when such temperatureis between about 1100 C. and about 1500 C. The temperature to which thereactant gas must be preheated in order to secure a reaction temperaturewithin this range depends upon a number of factors including thecomposition of the reactant gas, and the residence time within thepreheating zone. These factors are variables which contribute to thepossibility of reaction occurring between the reactant gas componentsduring the preheating in the absence of the added hydrogen. inasmuch asit is desirable to avoid such reaction, these variables should be socontrolled that the prehcat temperature is sufficient to attain thedesired subsequent reaction temperature but is not so high that reactionbetween the components of the reactant gas takes place to anysubstantial extent during the preheating. With reactant gas mixtures ofthe composition previously given it is usually desirable to preheat asrapidly as possible, e. g., in from about 0.005 to about 0.5 second.Thus, it is usually desirable to combine the components of the reactantgas prior to preheating the same, and to pass the mixture through thepreheating zone at a relatively high velocity. Under ordinary conditionsof operation the preheat temperature will be between about 600 C. andabout 1150 C. and the preheat time will be between about 0.1 and about0.005 second. Under any given set of conditions, the optimum preheattemperature for the present process will be somewhat higher than thatfor the hydrogenaddition process as previously practised.

The reaction time, i. e., the time interval between introduction of thepreheated reactant gas into the reaction zone and the cooling of theproduct gas to a temperature at which substantially no further reactionsoccur, varies inversely with the reaction temperature. Shorter reactiontimes are employed at the higher reaction temperatures within the givenrange, and vice versa. Such time is between about 0.001 and about 0.05second, preferably between about 0.002 and about 0.02 second, and isreadily controlled by varying the rate at which the gases Cil of thepattern.

are introduced into and are withdrawn from the reaction Zone. Thetemperature to which the product gas is cooled within such period oftime after introduction of the preheated reactant gas iirto the reactionzone is usually below about As will be seen from the foregoing, theprinciple of the invention resides in introducing a plurality of streamsof a preheated reactant gas comprising a hydrocarbon and oxygen into areaction zone and concurrently, in time as well as direction, therewithintroducing a hydrogencontaining gas adjacent the peripheral boundariesof said rone so that a gaseous lm comprising hydrogen is interposedbetween the body of reactant gas and said boundaries of the zone, whileobserving the operating conditions herein specied. Various ways ofapplying this principle will be apparent to those skilled in the art.Figures 3 and 4 diagrammatically illustrate a type of reactor suitablefor commercial application.

Referring now to Figures 3 and Il, in which like numerals designate likeparts, the reactor shown consists of a circular furnace 40, constructedof irebricl: or other refractory material, having a firebox ia definedby wall portions a roof portion 42, and floor portion 43. A relativelylarge circular opening M extends through roof portion e2, coaxial withthe vertical axis of the furnace, and directly below opening M anopening d5 or" equal size extends through floor portion 43. Opening tilis closed by a header it internally provided with upper supportingmembers ill' and 5,8. A lower supporting member te closes opening it atthe level of furnace floor Supporting members All and Q8 and 4S areperforated to receive and support reactant gas preheating tubes 50 andhydrogen-containing gas preheating tubes 5l parallel to each othervertically within Firebox e. Preheating tubes 50 and 5l are arranged ina concentric circular pattern, with the hydrogen-containing gaspreheating tubes 5i occupying the peripheral circle Header it isprovided with a transverse partition 52 which defines a reactant gasintroduction sone 53 communicating with reactant gas preheating tubes50, and a hydrogencontaining gas introduction zone 54 communieating withhydrogen-containing gas preheating tubes 5I. Reactant gas inlet manifold5S cornmunicates with reactant gas introduction zone 53 and a source ofreactant gas, not shown. Hydrogen-containing gas inlet manifold 50communicates with hydrogen-containing gas introduction zone 54 and asource of hydrogen-containing gas, not shown. Burners 5l communicatingwith a suitable fuel supply, not shown, are positioned Within rebox 00ctso as to supply heat to preheating tubes 50 and 5i, and a flue 5Bextends through furnace roof (l2 to provide an exit for the flue gasproduced by burners 5l. Floor portion G3 of furnace L10 is ofconsiderable thickness so that opening d5 which extends therethroughforms an elongated pasasgeway constituting a reaction Zone 59 into whichthe preheated gases are introduced from preheating tubes 50 and 5l.Since hydrogen-containing gas preheating tubes 5| are arranged aroundthe periphery of the circular pattern of tubes, the hydrogen-containinggas is necessarily introduced into reaction zone 59 immediately adjacentto the walls thereof and forms a gaseous layer or film between saidwalls and the streams of preheated reactant gas introduced into thereaction zone through tubes 50,

Quenching box 6U, which may be constructed of sheet metal, is positioneddirectly below furnace 40, and has an upper opening i coinciding withopening -45 in furnace Hoor 43. Spray nozzles 62 are positioned withinquenching box 00 so as to direct a liquid cooling medium, e. g. water,into the hot product gas issuing from reaction zone 59. A duct y53 isprovided for draining the cooling medium from the quench box, andproduct gas outlet S4 is provided for withdrawing the cooled product gasand passing it to storage means, not shown.

Operation of this reactor is substantially the same as that outlinedabove in connection with the reactor of Figures 1 and 2. The reactantgas passes from manifold 55 via introduction zone 53 through preheatingtubes 50 and into reaction zone 59. concurrently, thehydrogen-containing gas is introduced into manifold 55 and passes viaintroduction zone 50 through preheating tubes 5l and into reaction zone59. During pasasge through their respective preheating tubes thereactant and hydrogen-containing gases are heated to the requisitepreheat temperature by means of burners 51 which are supplied with asuitable fuel, e. g., fuel oil or natural gas, and air. Within reactionzone`59, the hydrogen-containing gas is for the most part interposed asa gaseous lm between the walls thereof and most of the reactant gas, andreaction occurs accompanied by an increase in` temperature as previouslydescribed. The velocity of the gases through the reactor is socontrolled that the hot product gas is cooled to a relatively lowtemperature by the cooling medium introduced through nozzles 62 withinthe short period of time herein specified. 'I'he cooled product gas iswithdrawn through outlet 64 and passed to suitable storage orseparatingmeans.

The following example will illustrate practice of the process of theinvention, but is not to be construed as limiting the same.

Example Reactant gas:

Methane 24.6% by vol. Air 73.4% by vol. Hydrogen-containing gas:

Hydrogen 95% by vol. Nitrogen 5% by vol. Rate of feed, reactant gas 62.6s. c. f./hr.

Rate of feed, hydrogen-containing gas 10.5 s. c. f./hr. Residence timein preheat zone 0.005 sec. Residence time in reaction zone 0.004 sec.

Mole ratio, hydrogen/methane 0.3/1 The yield of acetylene, based onmethane consumed, is about 4S per cent. Approximately one volume ofacetylene is formed per volume of hydrogen introduced into the reactionzone.

As will be apparent to those skilled in the art, many variations withrespect to different operating variables, reactor design, etc, arepossible within the herein defined scope of the invention, and variousengineering techniques may be applied to the practice of the inventionon a commercial scale. Thus for example, part of the preheating of thereactant gas and/or hydrogencontaining gas may be effected by indirectheat exchange against the product gas which, even though it has beenquenched within the reactor, is usually withdrawn therefrom at amoderately elevated temperature, e. g., 300-600 C. Various forms ofheaters and diiferent types of fuel may be employed for pre-heating, andthe reactor may take various forms adapted to conserve heat as much aspossible. Various refractory1 materials and heat-resistant metal alloysmay be employed in its construction. Likewise, the product gas may betreated in various known ways to separate the different constituentsthereof. The acetylene product may be separated by adsorption on a solidadsorbent, by selective solvent extraction, or by a selective chemicalreaction as by absorption in aqueous solutions of certain metal salts.The unreacted hydrocarbon may be recovered for reuse in the process byselective adsorption on activated charcoal, and the same type ofoperation may be employed to recover a hydrogen-containing gas suitablefor re-use in the process. Various hydrocarbon reactants may beemployed, although best results are attained with methane or naturalgas.

Other modes of applying the principle of my invention may be employedinstead of those explained, change being made as regards the materialsand apparatus employed, provided the steps stated by any of thefollowing claims, or the equivalent of such stated steps, be employed.

I, therefore, particularly point out and distinctly claim as myinvention:

l. In a process wherein (1) a reactant gas mixture essentiallycomprising a non-aromatic hydrocarbon having a normal boiling pointbelow about 400 F. and oxygen is preheated to a temperature below thatat which reaction spontaneously occurs between said hydrocarbon andoxygen but such that upon subsequent admixture of the preheated reactantgas with a hydrogencontaining gas comprising from about 30 to 100 percent by volume of molecular hydrogen and from about 70 to zero per centby volume of an inert gas there occurs an acetylene-producing reactionin which a temperature between about ll00 C. and about 1500 C. isattained, (2) the preheated reactant gas and a hydrogen-containing gasof the aforesaid composition are separately but simultaneouslyintroduced into a reaction zone, and (3) a product gas is withdrawn fromsaid reaction zone and is cooled to a temperature at which substantiallyno further reaction occurs, said cooling being effected within fromabout 0.001 to about 0.05 second after the introduction of the preheatedreactant gas into said reaction zone; the improvement which consists inintroducing the preheated reactant gas into said reaction zone in aplurality of separate streams, and introducing said hydrogen-containinggas into said reaction zone adjacent the boundaries thereof so as toprovide a gaseous film comprising the added hydrogen interposed betweensaid boundaries and said streams of preheated reactant gas.

2. A process according to claim 1 wherein the reactant gas comprisesoxygen and a normally gaseous saturated aliphatic hydrocarbon, the moleratio of hydrocarbon to oxygen being between about 1.33/1 and about3.0/1.

liliy 3'.: Alprocess.` accordingxtofclaim: 1 wherein thel reactant gascomprises'fromraboutl7 to about .305 percent by 1 volume offahydrocarbonselectedv from the class consistingrof methane and naturalgasandf from about 83'1to1ab`out170 per centby volumeof air.

4. A `process v according-Ito claiml wherein' the reactant gas ispreheatedtol'artemperaturebetween about 6009 C'.' and-about'l150tC.prior to its introduction into the reaction zone;

5. Alprocess according-to' hydrogen-.containing gas yis preheated tosubstantiallytthe same.;temperature` as the reactantgas prior toitsintroductioninto'the reaction zone.

G. A1process accordingfto'claiml:wherein the hydrogen-containinggas-comprises at least'about' 85per centbyvolume of freehydrogen andlless than about iper-cent by volume of a gas selected from the classconsisting otr.- nitrogen, carbon monoxide, and YYmixtures'of nitrogenand carbon monoxide;

7;' In a process whereinu) a reactantgas mixturev essentially comprising:arnormally4 gaseous saturated aliphatic hydrocarbon and oxygen in amolar ratio of 'between'ab'out' 1.33'fand vahoutflil passed through Vawhich is below. thatl-at which reactionspontaneously occurs betweenzsaidhydrocarbonaand oxygen, (2) the preheatedireactant*gas isintroL ducedinto an elongated:reactionvzone, (3)` an acetylene-producingreaction inAwhich aftern-A perature .betweenxab'outfllOOfi CJ andabout 1500 C. is`attained I is finitiatedf within said reaction Zone' by simultaneouslyintroducing'thereintoa hydrogen-containinggas.comprising :from aboutf30to 100 per cent by volumeof molecular hydro gen and fromabout'70tozero percent by volume of an inert gas,4 and..7 (4f) an'tacetyleneand hydrogen-containingproductgasis withdrawn from saidlreaction Zoney and cooled Yto a'temperature at' which substantially nofurther reaction occurs, said coolingk being eil'ected4 within from rentwith said- `strearnso'f preheated-reactant gas` so as to provide agaseousfhn comprising the added .hydrogen interposed'between saidboundaries and said streams:ofipreheatedreactant gas.

8; A process according. to claim- 7 wherein suicientof tthehydrogen-.containing gas is introduced into `the reaction'zzonetoprovide between about 0.1- and-about lxmole of hydrogen per mole of4hydrocarbonin the reactant gas.

9.v A process accordingitoclaim 7' wherein the reactant gascomprisesfrom about 17 to about 30 per cent by` volume of 'ashydrocarbon selected from the class consisting of methane and naturalgas and fromaboutfstoabout v70 per cent by volume of* air.

l0. A process according to claim 7 wherein the hydrogen-containing gasis preheatedV to substantially the sametemperatureasthe preheatedreactant gas prior to itsfintroduction into the reaction zone.

1l. A process according-to claim 7fwherein a claim il wherein ther molesofhydrocarb'on` perf mole' of" oxygenff ispreheatingezone wherein said"reactant `gas is preheated torai temperature which' i is-betweenaboutf600`CI and"ab`out`1l50f C". but

12 temperature betweenuabout1275 C.y andzabouttV 1375?. C.'ispermittedzto:beiattainediinthe acety'f lenehproducing: reaction' which'occurs withinA the:v reaction zone.

12; Aprocess accordingrtoclaim'7 whereinnthef product'gasis withdrawnfrom the reaction zoncv and cooledto a :temperature below about 600? CZwithin 1 from. about 0.002 to about-` 0.02 second. afterintroduction ofthe preheatedz'reactant.gasf into the. reaction zone;

13. Atprocess according to'` claim 7 whereinixthe: hydrogen-containinggas comprises at least about 2 per centby Volume' offreevhydrogen'andless thanzabout l'per cent by volume 'ora-.gas selectedfrom; ther class consisting.- of: nitrogen?.r carbon monoxide, and:mixtures of nitrogen and carbon monoxide.

14 In av process wl'ieren4 (l) a reactant gesl mixture essentially.comprising from .about117 to r aboutz30v per cent by; volume ofV ahydrocarbon.: selectedfromzthe class consisting'ot methane and. naturalgas and -from-about 83 -to yabout .7043er cent ley-volume of'airispassedthrough-apre h'eatingfzonefwherein-said reactant gas is preheated-:to atemperature which is between about 600- C. andabout l150 C. but which isbelow-- thatcat which reaction spontaneously'occurs betweensaidhydrocarbon and air,l (2) the pref heated-'i reactant gas Lis-introduced .into anelon. gatedzfreaction vzone,V (3) ahydrogen-containing.. gas:comprising.atfleastv aboutI 85 per cent by.volume of .free molecular hydrogen and lessthan. about .l5 percent byvolume of anY inert gasselectediromv the class consistingoffnitrogemcarbon monoxide; and :mixtures of nitrogen andcar-v bonAmonoxide isA passed .through a 1 secondpre.- heating Zone wherein saidhydrogen-containing. gasris preheated to substantially the sametemperature as the preheated reactant gas, (4) van. acetylene-producing.reaction in whichrva temperaturebetween about 1l00.` C. and about 15005.C. is attained isinitiated within said-reaction zone by introducingthereinto the preheated hydrogen-containing gas; and* (5) anacetyleneandihydrogenecontaining, product gas -is withdrawnfromAsaidreactiony zone'. and cooled (to, a. temperature belowabout' 600'"vC5., said cooling. being efiected'zwithin'rom about 0.002 and. about:0.02 'second after` thef'introduction ot they pre-r heated `reactant'gasinto said reaction zone; the improvement which consistsin introducingthey preheated; 1eactantgas into the axial portion ofsaid'reactionizonein at least four substantiallyV parallel `concurrent .separate streams,and intro-v ducing said preheatedr hydrogen-containing. gas. into saidreaction zone adjacent the peripheral boundaries thereof and concurrentwith said' streamsofpreheatedreactant gas so astoprovide a gaseous iilmcomprising the added hydrogen interposed between said boundariesandsaid' strearnof .preheated reactant gas.

References- Citedin the le of `this patentV UNITED STATES PATENTS NumberName Date 1,965,770 Burgin July l0, 1934A 1,965,771 Groll et al Julyl,1934 2,160,170 Martin et al. May 30, 1939 2,167,471 Auerbach July25,1939l 2,195,227 Sachsse Mar. 26, 1940 2,337,215V Krejci May 29, 1945FOREIGN PATENTS` Number Country Date-` 417033601 Gieat`Brtan Aug.; 13,.1937

1. IN A PROCESS WHEREIN (1) A REACTANT GAS MIXTURE ESSENTIALLYCOMPRISING A NON-AROMATIC HYDROCARBON HAVING A NORMAL BOILING POINTBELOW ABOUT 400* F. AND OXYGEN IS PREHEATED TO A TEMPERATURE BELOW THATAT WHICH REACTION SPONTANEOUSLY OCCURES BETWEEN SAID HYDROCARBON ANDOXYGEN BUT SUCH THAT UPON SUBSEQUENT ADMIXTURE OF THE PREHEATED REACTANTGAS WITH A HYDROGENCONTAINING GAS COMPRISING FROM ABOUT 30 TO 100 PERCENT OF VOLUME OF MOLECULAR HYDROGEN AND FROM ABOUT 70 TO ZERO PER CENTBY VOLUME OF AN INERT GAS THERE OCCURES AN ACETYLENE-PRODUCING REACTIONIN WHICH A TEMPERATURE BETWEEN ABOUT 1100* C. AND ABOUT 1500* C. ISATTAINED, (2) THE PREHEATED REACTANT GAS AND A HYDROGEN-CONTAINING GASOF THE AFORESAID COMPOSITION ARE SEPARATELY BUT SIMULTANEOUSLYINTRODUCED INTO A REACTION ZONE, AND (3) A PRODUCT GAS IS WITHDRAWN FROMSAID REACTION ZONE AND IS COOLED TO A TEMPERATURE AT WHICH SUBSTANTIALLYNO FURTHER REACTION OCCURS, SAID COOLING BEING EFFECTED WITHIN FROMABOUT 0.001 TO ABOUT 0.05 SECOND AFTER THE INTRODUCTION OF THE PREHEATEDREACTANT GAS INTO SAID REACTION ZONE; THE IMPROVEMENT WHICH CONSISTS ININTRODUCING THE PREHEATED REACTANT GAS INTO SAID REACTION ZONE IN APLURALITY OF SEPARATE STREAMS, AND INTRODUCING SAID HYDROGEN-CONTAININGGAS INTO SAID REACTION ZONE ADJACENT THE BOUNDARIES THEREOF SO AS TOPROVIDE A GASEOUS FILM COMPRISACTANT GAS.